Leary understood something that many scientists, researchers and intellectuals have since come to understand, but a far greater number fail to comprehend/refuse to acknowledge/are simply insufficiently equipped to furnish themselves with this universal law upon which successful engagement between practitioner and patient (in the therapeutic use of psychedelics) depends.
To be effective in their role, the practitioner must step across the line momentarily, entering this mystical realm that has been a constant in spiritual, psychic, physical and mental wellness throughout the ages of man and beyond. Doing so permits a connection with the patient and the universe/God/Nature/reality- however your personal tenet describes it.
Psychedelics have been lumped together under the umbrella that is known as "evil illicit drugs". Worse than that, because they're perceived as being potentially antisocial -societal cogs will grind to a halt when too many people reject the position they've been primed to adopt with all its responsibilities - instead choosing to "tune in, turn on and drop out".
Like countless pioneers who went before him, he suffered at the hands of those who would make an example of him - yet defiance fuelled by his resounding convictions, he pioneered a regard for these substances and continued research that (despite exceptional judicial and political measures- not to mention widespread hysteria and condemnation thanks to media demonisation) persisted just beneath the radar and only now 70 years later, is under consideration for its medicinal applications.
The epic number of people who suffered unduly because of the ridiculous overreach of certain influential bodies during those years is a disgrace. Had they simply permitted Dr Leary the "free speech" that the US proudy proclaims as applicable to all citizens, perhaps this world might just have been a slightly nicer place today.